Nervous System Flashcards

Question

Threshold

Answer 1

Must be reached for nerve impulse to begin Enough Na+ or Ca+ must enter the neuron (GRADED POTENTIAL) from the dendrites and cell body to push the membrane potential to the threshold for firing at the axon hillock (All or none law: either an impulse or not, there’s no weaker impulse, always same amplitude)

Answer 2

After threshold, sodium/calcium ions entering very quickly Voltage gated sodium ion channels, follows concentration gradient

Answer 3

Small amounts of Na+ or Ça+ entering before threshold Enough graded potential to hit threshold Occurs in dendrite and cell body, if enough, then it reaches the hillock

Answer 4

Goes back down, potassium ions leaving axon Voltage gated potassium ion channels

Answer 5

Reaches threshold Depolarization Repolarization Hyperpolarization (relative refractory period) Back at resting membrane potential Goes in a wave Does not diminish, once started Does not vary in intensity if the stimulus is stronger (all or none law)

Answer 6

Absolute refractory period: after voltage Na channels open, they close (inactive phase) and cannot be opened again no matter the stimulus strength. Serves to keep the direction of the action potential from axon hillock→axon terminals (unidirectional) Relative refractory period: hyperpolarization and a bit before, partway through repolarization, enough Na+ channels come out of their inactive phase and a large stimulus (greater than threshold) may elicit another impulse during the relative refractory period

Answer 7

Nerve impulse will allow for Ça+ channels to open, which lets the neurotransmitter vesicle bind to presynaptic membrane and release the neurotransmitters into the synaptic cleft, bind with receptors on the membrane of the postsynaptic neuron. This causes an ion channel on the postsynaptic membrane to open Synapse: junction where an impulse is transmitted between a neuron and another cell Chemical impulse Occurs by neurotransmitters: chemical messengers stored in and released from axon terminals. responsible for transmitting (or terminating) the nerve impulse to the next cell Neurotransmitters diffuse across the gap In the case of two neurons, the presynaptic neuron releases a neurotransmitter to the postsynaptic neuron

Answer 8

Synaptic vesicles Synaptic knob: swelling at the end of the axon terminal of the presynaptic neuron Synaptic cleft Postsynaptic neuron has ion channels with receptors for neurotransmitters I

Answer 9

Temporary presence in synaptic cleft, will bind to post synaptic neuron and then be removed very fast, Some are deactivated by enzymes: – For example, the enzyme acetylcholinesterase removes acetylcholine from synapses • Others are pumped back into the synaptic knob of the presynaptic axon

Answer 10

If excitatory synapse, binding of the neurotransmitter to the receptor on the postsynaptic neuron produces an excitatory postsynaptic potential (EPSP), increasing the chance that an action potential will begin (closer to threshold At an inhibitory synapse, binding of a different neurotransmitter to the receptor on the postsynaptic neuron produces an inhibitory postsynaptic potential (IPSP), decreasing the chance that an action potential will begin (more negative) (either negative ions go in or positive ions leave) Some have 1 synapse, some have the other, some both Summation EPSP and IPSP will determine whether an action potential is generated, this level of integration fine control of neuronal responses

Answer 11

Temporal: one presynatpic neuron sending many signals to a post synaptic neuron. How quickly and how many times is 1 synapse firing Spatial: many presynatic neurons sending signal/s to a post synaptic neuron. Count number of inhibitory and excitatory.

Answer 12

Classified as Inhibitory (hyperpolorizstion) and excitatory (depolarization) Acetylcholine: mostly excitatory but inhibitory neuromuscular synapses at heart. Activates all voluntary muscles

Answer 13

Direct: Ligand gated channels: neurotransmitters binds and allows a positive ion channel (almost always Ca2+ or Na+) to open (ex serotonin and acetylcholine Indirect: neurotransmitter binds to receptor and G protein activated, G protein subunit or intra cellular messenger modulâtes ion channel (ex glutamate, GABA

Answer 14

Difference is receptors Ex acetylcholine, excitatory at neuromuscular junctions, inhibitory between the vagus nerve and cardiac muscle Other ex: blushing and adrenegic synapse Veins in your face have beta adrenergic (norepinephrine) receptors, blood vessels dilate Other veins in your body are mostly alpha receptors, where blood vessels constricts and send it towards the heart

Answer 15

Agonist: drug that mimics the effect of a neurotransmitter Antagonis: a drug that blocks the effect of the neurotransmitter Nicotine is agonist of acetylcholine. when bound to the nicotinic receptor, activates muscles to contract curare is antagonist of acetylcholine. when bound to the nicotinic receptor, prevents muscles to contract Muscarine is agonist of acetylcholine, slows down your heartrate when bound to muscarinic receptor. atropine is antagonist of acetylcholine, speed up your heart rate when bound to muscarinic receptor. Morphine & heroin (opioid drugs) are agonists of our endorphins. When they bind to opioid receptors, they block the sensation of pain Caffeine is an antagonist of adenosine. Adenosine receptors when bound to adenosine depresses brain activity and allows us to sleep. Benzodiazapines (eg. Valium) are agonists of GABA. When they bind to GABA receptors, they promote sedative effects, and may also cause other effects such as anticonvulsant and muscle relaxant effects

Answer 16

Rapid, predictable and involuntary motor responses to stimuli Occurs over neural pathway called reflex arc Somatic reflexes: activates skeletal muscles, ex pulling your hand away from a hot object Autonomic: smooth muscle, hearts and glands

Answer 17

Sensory receptors Sensory neuron Integrating center Motor neuron Effector

Answer 18

2 neuron reflex arc (knee jerk) 3 neuron reflex arc (flexor reflex, pulling hand away from fire) Emesis (vomiting) reflex

Answer 19

Cranial nerves: take impulse to and from the brain Spinal nerves: take impulses to and away from the spinal cord and brain Ganglia: collections of nerve cell bodies

Answer 20

Connects right and left hemisphere

Answer 21

Integrate skin and muscle near your brain 12 pairs of cranial nerves primarily serve the head and neck Most of them are mixed Vagus nerves (10) is the only pair that extends to the thoracic and abdominal cavity 3 nerves purely sensory: 1: olfactory (what you’re smelling) 2: optic 8: vestibulocochlear (ears and balance)

Answer 22

only pair of cranial nerves that extend beyond the head and neck region Most motor fibers are parasympathetic fibers that signal to the heart, lungs, and abdominal viscera Sensory fibers carry impulses from thoracic and abdominal viscera, baroreceptors, chemoreceptors, and taste buds

Answer 23

31 pairs of mixed spinal nerves Cervicales, thoracic, lumbar, cauda equina/sacrale reagion (inferior ends) Structure: enters dorsal side, integrated in gray matter of spinal cord, gets out on the ventral side Dorsal horn: contain cell bodies of interneurons, gray matter Dorsal root: receive info for dorsal horns, Dorsal root ganglion: ganglion on dorsal side, cell body housed there Ventral horns: contain cell bodies of motor neurons of the somatic nervous system, Send information out ventral root Everything surrounded

Answer 24

We integrate information coming from one side of our body will be integrated on the opposite side of our brain

Answer 25

Ventral and dorsal root emerging from spinal cord merge to form the spinal nerve Almost immediately, the spinal nerve (only ~1 cm long) separates into a dorsal ramus and a ventral ramus Ventral ramus • Ramus: branch of a spinal nerve; contains both motor and sensory fibers DORSAL RAMI: serve the skin and muscles of the posterior trunk • VENTRAL RAMI (T1–T12): form the intercostal nerves that supply muscles and skin of the ribs and trunk VENTRAL RAMI (except T1–T12): form a complex of networks (plexus) of sensory and motor nerves for the limbs

Answer 26

Branches from adjacent spinal nerves that will reorganize themselves into braid looking to redistribute where the sensory and motor neurons will go 4 voluntary plexuses: cervical plexus: headm neck, shoulders, diaphragm branchial plexus: upper limbs, neck, shoulder muscles lumbar plexus: abdominal wall, external general and lower limbs sacral plexus: buttocks, perinieum, lower limb

Answer 27

the somatic and autonomic nervous systems differ: 1) in their effectors 2) in their efferent pathways 3) in target organ responses to their neurotransmitter Parasympathetic and sympathetic nervous systems are always operating at varying degree, but there is a dominant one. Parasympathetic is less physiologically demanding, so body prefers it.

Answer 28

Motor neurons originate in the CNS, axons extend to skeletal muscles, 1 neuron releases acetylcholine in the end

Answer 29

Chain of two motor neurons Preganglionic neuron is in the brain or spinal cord Postganglionic neuron extends to the organ (no myelin) Parasympathetic: long preganglionic, releases acetylcholine at both neurons. Often come from cervical and cranial region Sympathetic: often come from lumbar and thoracic region. (T1 to L2) short preganglionic, releases acetylcholine at the ganglion, releases norepinephrine in the end Or 1 Neuron goes to adrenal medulla, release acetylcholine into adrenal medulla, signal it to release epinephrine and norepinephrine into blood vessel

Answer 30

Cholinergic (parasympathic) postganglion fibres: release acetylcholine Adrenergic (sympathic) postganglion fibres: release norepinephrine, epinephrine or dopamine Synalthetic and parasympathetic systems have antagonistic effects due to different neurotransmitters

Answer 31

Only have intervention from sympathetic nervous system

Answer 32

Groups of ganglions connected in a trunk (22 pairs of ganglia)

Answer 33

White ramus communicans: contains axons of 1st motor neuron of the pathway, so it is myelinated and will appear white Grey ramus communicans: contains axons of 2nd motor neuron of the pathway, so it is not myelinated and will appear grey preganglionic neuron leaves the lateral horn using the ventral horn, messages goes through there to the white ramus, then enter the sympathic trunk, then leaves via the grey ramus (post ganglionic at that point) either at the same level or another level, then leaves via the ventral ramus to supply its target organ

Answer 34

Preganglionic neurons originate in: – Cranial nerves III, VII, IX, and X – S2 through S4 regions of the (sacral) spinal cord Preganglionic neurons synapse with terminal ganglia; from there, postganglionic axons extend to organs that are served Its autonomic (terminal) ganglia are located on or near the effector organ Both pre- and postganglionic neurons have cholinergic fibres

Answer 35

Parasympathetic: vagus nerve releases acetylcholine, relax heart Sympathetic: acce,realtor nerve releases norepinephrine, go up

Answer 36

enhances neurotransmitter action amphetamunes anc cocaines inhibits re-uptake of serotonin, norepinephrine and dopmine selective serotonin reuptake inhibitor (SSRI): antidepressant

Answer 37

inhibit release or productin of a neurotransmitter reserpine: depletes epinephrine and norepinephrine from synapses to treat hypertension

Answer 38

alzheimers: brain atrophy (becomes smaller) associated with decreased levels of acetylcholine clinical depression: associated with decreased levels of serotonin, dopamine and norepinephrine parkinsons: affects the nerve cells in the brain that produce dopamine